ENH: Improve dtype typing and testing

Author: Kevin Sheppard

pandas-stubs/core/arrays/boolean.pyi

@@ -1,24 +1,11 @@
 import numpy as np
 
-from pandas._typing import (
-    Scalar,
-    type_t,
-)
-
 from pandas.core.dtypes.base import ExtensionDtype as ExtensionDtype
 
 from .masked import BaseMaskedArray as BaseMaskedArray
 
 class BooleanDtype(ExtensionDtype):
     name: str = ...
-    @property
-    def na_value(self) -> Scalar: ...
-    @property
-    def type(self) -> type_t: ...
-    @property
-    def kind(self) -> str: ...
-    @classmethod
-    def construct_array_type(cls) -> type_t[BooleanArray]: ...
     def __from_arrow__(self, array): ...
 
 def coerce_to_array(values, mask=..., copy: bool = ...): ...

pandas-stubs/core/dtypes/dtypes.pyi

@@ -93,8 +93,6 @@ class PeriodDtype(PandasExtensionDtype):
     def construct_from_string(cls, string: _str): ...
     @property
     def name(self) -> _str: ...
-    @property
-    def na_value(self): ...
     def __hash__(self) -> int: ...
     def __eq__(self, other) -> bool: ...
     @classmethod